The Valley of the Kings, on the West Bank of the Nile, is the burial ground of the great Pharaohs of the Empire. Beginning with the 18th Dynasty and ending with the 20th, the kings abandoned the Memphis area and built their tombs in Thebes. Also abandoned were the pyramid style tombs. Most of the tombs were cut into the limestone following a similar pattern: three corridors, an antechamber and a sunken sarcophagus chamber. These catacombs were harder to rob and were more easily concealed. Construction usually lasted six years, beginning with the new reign. There have been 64 tombs discovered to date.